This invention is in the field of removing surfactants (predominantly sulfonates) from hydrocarbons particularly those in the gasoline or kerosene boiling range by mixing the hydrocarbons with alcohol followed by water washing.
It has been found that surfactants in gasoline can cause automobile fuel filter plugging, which can be very disconcerting to customers whose cars stall at inconvenient times. It is, of course, preferable that the various gasoline blending components not contain such surfactants. However, certain of these components, particularly alkylate, have a tendency to become contaminated with surfactants, such as sulfonates, during refinery processing. Where such contamination has occured, it is highly desirable to remove the contaminants as efficiently as possible.
A method of removing metal alkaryl sulfonates from crude oil is disclosed in U.S. Pat. No. 4,274,943. The crude oil containing the metal alkaryl sulfonates is treated by (a) contacting it with an aqueous basic solution containing a "recovery surfactant", (b) forming a hydrocarbon phase and an aqueous phase containing the metal alkaryl sulfonates and (c) separating the hydrocarbon phase and the aqueous phase. "Recovery surfactants" include ethoxylated alcohols, ethoxylated alkylphenols, ethoxylated alcohol sulfates, polyoxyethylene-polyoxypropylene block polymers, and ethoxylated polypropylene glycols. The alkyl group in these "recovery surfactants" contains from 10-20 carbon atoms. While this process may be effective for removing metal alkaryl sulfonates from crude oil it is not considered suitable for removing surfactants from gasoline boiling range components.
Alkylate cleanliness has long been recognized as a problem in gasoline blending. Because the reactions involved in the manufacture of alkylate are conducted in the presence of sulfuric acid, all manner of sulfur and oxygen containing compounds may potentially be formed and become part of the alkylate stream. Caustic and water wash systems have been installed in alkylation units to reduce the level of contaminants in alkylate. These systems must be periodically checked, however, to insure their proper operation. Surfactants, if allowed to accumulate in storage systems, will migrate to the aqueous phase in storage tanks. When the tank contents are stirred up as they are, for example, during filling, these surfactants will tend to keep particulate matter and gelatinous material suspended in the product and thus increase the potential for carrying these materials either into the pipeline or at the extreme into automobile fuel tanks. It is important, therefore, that alkylate be treated as severely as necessary to reduce these surfactant levels in the finished product.
Accordingly, it is an object of this invention to provide a method for removing hydrocarbon-soluble anionic surfactants from gasoline or kerosene boiling range hydrocarbons.